So-called "lithium" batteries are known in the art and take a variety of forms. Typically they include essentially: an electrode (i.e., anode) comprising lithium or alloys thereof (e.g., Li-Al); a lithium ion conducting electrolyte; and a counter-electrode (i.e., cathode) comprising any of a number of materials such as titanium disulfide, molybdenum disulfide, manganese dioxide, or vanadium oxide (V.sub.6 O.sub.13). As used herein, the term "lithium" is intended to include not only pure lithium but alloys thereof useful in lithium batteries. High temperature (i.e., Ca. 300.degree. C.) lithium batteries often use so-called glassy electrolytes comprising various oxide mixtures such as (1) lithium oxide and aluminum oxide, 2) lithium oxide and silicon dioxide, (3) lithium oxide, silicon dioxide and zirconium oxide or (4) lithium oxide, silicon dioxide and phosphorous oxide (PO.sub.3). Moderate temperature (i.e., Ca. 100.degree. C.) lithium batteries may use a viscous polymer electrolyte such as (1) lithium perchlorate dissolved in polyethylene oxide or (2) 2-2-methoxy-ethoxy-ethoxypolyphosphazene (i.e., aka MEEP). A known room temperature lithium battery uses a non-aqueous, liquid organic electrolyte comprising lithium salt dissolved in propylene carbonate. None of the aforesaid batteries utilize a solid-state electrolyte and their operating temperatures and/or liquid electrolyte limits their usefulness.
A solid-state, lithium battery has been suggested which utilizes lithium nitride as the electrolyte. Unfortunately, lithium nitride has relatively low ion transport properties at room temperatures and electrochemically decomposes when cell voltages exceed about 0.4 volts. Hence not only are lithium nitride cells current limited but can only be made with cathode materials which yield cell voltages less than the 0.4 volts decomposition voltage. This latter limitation eliminates the aforesaid more popular cathode materials all of which yield significantly higher cell voltages. Higher voltages are, of course, more desirable for most applications.
It is an object of the present invention to provide a lithium battery having a unique, solid-state electrolyte which not only has high room temperature ionic conductivity but which is electrochemically stable against decomposition at relatively high cell voltages. This and other objects and advantages of the present invention will become more readily apparent from the detailed description thereof which follows and which is given hereafter in conjunction with the several drawings in which: